JP6460031B2 - Sheet conveying apparatus and image forming apparatus provided with sheet conveying apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus that conveys the uppermost sheet by separating and conveying the uppermost sheet from a sheet bundle made up of a plurality of sheets fed from a sheet storage unit, and an image forming apparatus including the same.

  The image forming apparatus includes a sheet conveying device that conveys a sheet such as paper. The sheet conveying device feeds the uppermost sheet stored in the sheet storing unit in the feeding direction by a pickup roller, and feeds the sheet to the conveying path by a feeding roller located on the downstream side thereof. In this type of sheet conveying apparatus, there is a case where so-called double feeding occurs in which a plurality of sheets are picked up and sent out by a pickup roller. 2. Description of the Related Art Conventionally, as a mechanism for preventing double feeding, a separation mechanism using separation rollers that face each other while being in contact with the feeding roller is known. In the separation mechanism, a nip portion in a predetermined range is formed between the feeding roller and the separation roller by the separation roller coming into contact with the feeding roller. When a plurality of sheets are fed to the nip portion, the separation mechanism separates only the uppermost sheet from the plurality of sheets and feeds it to the feeding roller. Further, as an example of the image forming apparatus provided with the separation mechanism, the feeding roller and the separation roller are moved at a timing when the sheet that has passed through the separation mechanism reaches the conveyance roller on the downstream side in the feeding direction. An image forming apparatus to be separated is known (see Patent Document 1).

JP 2011-126626 A

  By the way, there is a case where the rotation of the separation roller stops and the uppermost sheet is separated in a state where the leading edge of the lower sheet is in contact with a part of the nip portion. In this case, since the lower surface (back surface) of the uppermost sheet is in contact with the outer peripheral surface of the separation roller in the nip portion, the lower surface of the uppermost sheet and the outer peripheral surface of the separation roller are conveyed by the downstream conveying roller. Slid in contact with each other and stick slip occurs, and abnormal noise due to the stick slip occurs. This abnormal noise can be suppressed by separating the feeding roller and the separation roller during conveyance by the conveyance roller. However, after the feeding roller and the separation roller are separated from each other, the lower side sheet is separated from the nip portion of the separation mechanism by the inter-sheet friction as the uppermost sheet is conveyed by the conveyance roller. May be pulled out. When the drawn sheet reaches the transport roller on the downstream side, there is a problem that the sheet is double-fed by the transport roller.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress noise during sheet conveyance and to prevent double feeding of sheets after the separation roller is separated and the nip is released. It is an object of the present invention to provide a sheet conveying apparatus and an image forming apparatus that can perform the above operation.

  A sheet conveying apparatus according to one aspect of the present invention includes a sheet storage unit, a first conveying roller, a separation roller, a support member, a second conveying roller, a displacement mechanism, and a stop member. The sheet accommodating portion is configured to accommodate a plurality of sheets. The first conveying roller conveys the sheet in the sheet conveying direction by being rotationally driven while being in contact with the sheet fed in a predetermined sheet conveying direction from the sheet storage unit. The separation roller is provided below the first conveyance roller, and is separated from a sheet bundle composed of a plurality of sheets fed from the sheet storage unit in a state where a nip portion is formed in contact with the first conveyance roller. The upper sheet is separated at the nip portion. The support member rotatably supports the separation roller, and the separation roller serves as the first conveyance roller around a swing shaft that is positioned downstream of the first conveyance roller in the sheet conveyance direction. The separation roller is supported so as to be swingable between a first position where the nip portion can be formed by contact and a second position where the separation roller is separated from the first transport roller. The second conveying roller is provided downstream of the first conveying roller in the sheet conveying direction, and is rotated to convey the sheet conveyed by the first conveying roller in the sheet conveying direction. . The displacement mechanism displaces the support member to the first position during a transport operation by the first transport roller, and displaces the support member to the second position during a transport operation by the second transport roller. The stop member is provided on the support member, and when the support member is located at the second position, the sheet is transported from the first transport roller along with the transport of the uppermost sheet by the second transport roller. The lower sheet is brought into contact with the lowermost sheet than the uppermost sheet pulled out in the conveying direction, and the conveyance of the lower sheet is stopped.

  An image forming apparatus according to another aspect of the present invention includes the sheet conveying device and an image forming unit that forms an image on a sheet conveyed by the sheet conveying device.

  According to the present invention, it is possible to suppress abnormal noise during sheet conveyance, and to prevent double feeding of sheets after the separation roller is separated and the nip is released.

FIG. 1 is a perspective view showing a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing an internal configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is an enlarged view showing the configuration of the sheet feeding device according to the embodiment of the present invention. FIG. 4 is a schematic diagram illustrating a positional relationship between a retard roller and a retard holder included in the sheet feeding device according to the embodiment of the present invention. FIG. 5 is a diagram illustrating a transmission mechanism provided in the sheet feeding device according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. Embodiment described below is only an example which actualized this invention, and does not limit the technical scope of this invention. For convenience of explanation, the vertical direction is defined as the vertical direction D1 in the installation state in which the image forming apparatus 10 can be used (the state shown in FIG. 1). Also, the front-rear direction D2 is defined with the front surface (front surface) on which the paper cassette 30 shown in FIG. Further, the left-right direction D3 is defined with reference to the front of the image forming apparatus 10 in the installed state.

  Hereinafter, the configuration of the image forming apparatus 10 will be described.

  The image forming apparatus 10 according to the embodiment of the present invention is an apparatus having at least a printing function. The image forming apparatus 10 is a so-called tandem type color printer.

  As shown in FIGS. 1 and 2, the image forming apparatus 10 includes a housing 11. The housing 11 has a substantially rectangular parallelepiped shape as a whole. Inside the housing 11, each part constituting the image forming apparatus 10 is disposed.

  As shown in FIG. 2, the image forming apparatus 10 includes four image forming units 4, an intermediate transfer belt 5, an optical scanning device 13, a secondary transfer roller 20, a fixing device 16, a paper discharge tray 18, and a paper feeding device 24. , A registration roller pair 29 (an example of the second transport roller of the present invention), an operation display unit 25 (see FIG. 1), a belt cleaning device 6, and a control unit 2 that controls the image forming apparatus 10 in an integrated manner. The image forming unit 4, the intermediate transfer belt 5, the secondary transfer roller 20, and the fixing device 16 are examples of the image forming unit of the present invention. Further, the sheet feeding device 24 and the registration roller pair 29 realize the sheet conveying device of the present invention.

  Each of the image forming units 4 includes a photosensitive drum, a charging device, a developing device, a primary transfer roller, and the like, and forms an image on the intermediate transfer belt 5 according to an electrophotographic system. The image forming units 4 are arranged in parallel along the front-rear direction D2 inside the housing 11, and form a color image based on a so-called tandem method. The image forming unit 4 superimposes and transfers each color toner image on the intermediate transfer belt 5 to form a color toner image on the intermediate transfer belt 5. The toner image on the intermediate transfer belt 5 is transferred by the secondary transfer roller 20 to a sheet (an example of the sheet of the present invention) fed from the sheet feeding device 24.

  The intermediate transfer belt 5 is provided above the four image forming units 4. The intermediate transfer belt 5 is rotatably supported by a driving roller 5A and a driven roller 5B. By being supported by the driving roller 5A and the driven roller 5B, the intermediate transfer belt 5 can move in the direction of the arrow 19 while the surface thereof is in contact with the surface of each photosensitive drum.

  The optical scanning device 13 is provided below the four image forming units 4. The optical scanning device 13 forms an electrostatic latent image on each photoconductive drum by irradiating the photoconductive drum of each image forming unit 4 with laser light based on the input image data of each color.

  The paper feeding device 24 is provided at the bottom of the housing 11. The sheet feeding device 24 includes a sheet feeding cassette 30 (an example of a sheet storage unit of the present invention) and a feeding mechanism 50. A plurality of sheets of a prescribed size are stored in the sheet feeding cassette 30. On the rear side of the housing 11, a conveyance path 26 is formed from the paper feeding device 24 through the secondary transfer roller 20 to the fixing device 16. The feeding mechanism 50 is provided on the rear side of the paper feeding cassette 30, takes out the sheets stacked in the paper feeding cassette 30 one by one, and feeds them toward the conveyance path 26. Accordingly, the sheet is conveyed along the conveyance path 26 in the sheet conveyance direction from the feeding mechanism 50 toward the secondary transfer roller 20. The detailed configurations of the paper feed cassette 30 and the feed mechanism 50 will be described later.

  As shown in FIG. 2, a registration roller pair 29 is provided in the vicinity of the conveyance path 26. Specifically, the registration roller pair 29 is provided on the downstream side in the sheet conveyance direction from the feeding mechanism 50 of the sheet feeding device 24. The registration roller pair 29 includes a driving roller 29A that is rotationally driven by the control unit 2 and a driven roller 29B that is driven by contacting the driving roller 29A. The sheet fed to the conveyance path 26 by the sheet feeding device 24 is conveyed to the secondary transfer roller 20 by the registration roller pair 29.

  The secondary transfer roller 20 is provided downstream of the registration roller pair 29 in the sheet conveyance direction on the rear side of the housing 11. The secondary transfer roller 20 is provided at a position facing the drive roller 5A. A toner image is transferred from the intermediate transfer belt 5 to the sheet by the secondary transfer roller 20.

  The fixing device 16 is provided on the upper side of the secondary transfer roller 20. The fixing device 16 includes a heating roller 16A, which is a pair of rollers, and a pressure roller 16B. The pressure roller 16B is urged by an unillustrated elastic member (for example, a spring) and is in pressure contact with the surface of the heating roller 16A. The fixing device 16 conveys the sheet while sandwiching the sheet by the heating roller 16A and the pressure roller 16B. At this time, heat is transmitted from the heating roller 16A to the sheet, and the toner on the sheet is melted and fixed on the sheet. Thereby, a color image is formed on the paper.

  A discharge path 28 is formed between the fixing device 16 and the sheet discharge port 27. The sheet that has passed through the fixing device 16 is conveyed through a discharge path 28 by a discharge roller 23 and discharged from a sheet discharge port 27 to a discharge tray 18.

  Hereinafter, the configuration of the paper feed cassette 30 will be described.

  The paper feed cassette 30 is supported by the housing 11. In the present embodiment, the paper cassette 30 is supported by the housing 11 so as to be slidable in the front-rear direction D2. As a result, the paper feed cassette 30 can move between a position housed in the housing 11 and a position pulled forward from the housing 11.

  The paper feed cassette 30 is formed in a rectangular box shape having a bottom surface 34. A plurality of sheets can be stored in the sheet feeding cassette 30. A lift plate 32 is provided on the bottom surface 34 of the paper feed cassette 30, and the lift plate 32 is supported so that the front end portion can be raised from the rear end side. When a driving force is input to the lift plate 32, for example, when the motor is driven and controlled by the control unit 2, the lift plate 32 starts to rise, and the uppermost sheet in the paper cassette 30 can be fed. Raised to feed position. A sensor (not shown) is provided above the paper feed cassette 30. When the lift plate 32 rises to the feeding position, the control unit 2 receives the output signal of the sensor and stops the lift plate 32 from rising. To do. When the amount of sheets loaded in the sheet feeding cassette 30 decreases and the position of the uppermost sheet is lowered, the lift plate 32 is raised again and stopped at the feeding position. By performing such lift control of the lift plate 32, the uppermost sheet in the sheet feeding cassette 30 is always arranged at the feeding position.

  Hereinafter, the feeding mechanism 50 will be described.

As shown in FIG. 2, the feeding mechanism 50 is provided above the rear end portion 31 of the paper feeding cassette 30. The feeding mechanism 50 includes a pickup roller 51, a feed roller 52 (an example of a first transport roller of the present invention), a paper feed holder 55, a retard roller 53 (an example of a separation roller of the present invention), and a retard holder 60. (An example of a support member of the present invention) and a coil spring 72 as an urging member for applying an urging force to the retard holder 60.
It has.

  The pickup roller 51 is rotatably supported by the paper feed holder 55. The pickup roller 51 includes a rotation shaft 51A (see FIG. 3) extending in the left-right direction D3, and the rotation shaft 51A is rotatably supported by the paper feed holder 55. As shown in FIG. 3, the paper feed holder 55 is supported so as to be positioned above the paper feed cassette 30. Specifically, the pickup roller 51 is disposed at a position where the roller surface comes into contact with the uppermost sheet stored in the sheet feeding cassette 30. When a predetermined rotational driving force is input to the rotating shaft 51A and the pickup roller 51 is rotationally driven, the pickup roller 51 applies a feeding force due to contact friction to the uppermost sheet pushed up by the lift plate 32. To do. Thereby, the pickup roller 51 sends out the sheet toward the feed roller 52 on the downstream side in the feeding direction by the pickup roller 51 (corresponding to the sheet conveying direction of the present invention).

  As shown in FIG. 3, the feed roller 52 includes a rotation shaft 52 </ b> A that is parallel to the rotation shaft 51 </ b> A of the pickup roller 51. The rotation shaft 51 </ b> A is rotatably supported by the inner frame of the housing 11. In the present embodiment, the paper feed holder 55 is swingably supported at both ends of the rotation shaft 52A. That is, the rotation shaft 52A also serves as the swing shaft of the paper feed holder 55. The feed roller 52 is disposed downstream of the pickup roller 51 in the delivery direction. For this reason, the paper feed holder 55 is supported by the rotation shaft 52A, so that the pickup roller 51 side can swing around the rotation shaft 52A. Specifically, the paper feed holder 55 can swing in a direction in which the roller surface of the pickup roller 51 is in contact with or separated from the uppermost sheet.

  The feed roller 52 is disposed at a position where the roller surface comes into contact with the upper surface of the sheet fed by the pickup roller 51. When the rotational driving force from the motor is input to the rotation shaft 52A and the feed roller 52 is rotationally driven, the feed roller 52 rotates in contact with the paper fed by the pickup roller 51, and is fed by the contact friction. A feeding force is applied to the sheet, and the sheet is fed to the downstream conveyance path 26 (see FIG. 2). A transmission mechanism such as a gear or a belt is interposed between the rotation shaft 52A of the feed roller 52 and the rotation shaft 51A of the pickup roller 51, and the rotational driving force input from the motor to the rotation shaft 52A is It is transmitted to the rotating shaft 51A via the transmission mechanism.

  The retard roller 53 is provided below the feed roller 52. The retard roller 53 is supported by a retard holder 60 described later. By being supported by the retard holder 60, the retard roller 53 comes into contact with the roller surface of the feed roller 52 and forms a nip portion 79 (see FIG. 3) with the feed roller 52. When the plurality of sheets are fed out in a bundle by the pickup roller 51 at a time, the retard roller 53 is lower than the uppermost sheet P1 (see FIG. 4) of the plurality of sheets. It is used for the purpose of separating other paper P2 (see FIG. 4). The retard roller 53 and its support mechanism will be described later.

  An elastic member 58 having a predetermined hardness is provided on the outer periphery of the retard roller 53. The elastic member 58 is smaller than the hardness of the surface of the feed roller 52, and, for example, urethane rubber having an elastic force measured by a durometer type A type rubber hardness tester defined in JIS standards within a range of 25 to 50 degrees. It consists of That is, the outer peripheral surface of the retard roller 53 is formed of a material that is softer and more elastic than the surface of the feed roller 52. The hardness of 25 degrees to 50 degrees is an example, and the elastic member 58 only needs to have a hardness smaller than the hardness of the surface of the feed roller 52. The elastic member 58 may be made of a material other than urethane rubber, such as nitrile rubber, chloroprene rubber, or silicon sponge.

  A torque limiter 74 is provided inside the retard roller 53. The torque limiter 74 is attached to the rotation shaft 53A of the retard roller 53, and is interposed between the rotation shaft 53A and the retard roller 53. The torque limiter 74 idles the retard roller 53 with respect to the rotating shaft 53A when the retard roller 53 receives a torque (an example of the set torque of the present invention) having a magnitude equal to or larger than a predetermined torque set value Ft. .

  As shown in FIG. 3, the retard holder 60 rotatably supports the retard roller 53. Specifically, the retard holder 60 has an accommodating portion 61 that accommodates the retard roller 53. The retard roller 53 has a rotation shaft 53 </ b> A that extends in the same direction as the axial direction of the pickup roller 51 and the feed roller 52. The rotation shaft 53A is fixedly supported by a shaft hole (not shown) provided in the side wall 63 of the housing portion 61 in the left-right direction D3. The retard roller 53 is rotatably supported by a rotating shaft 53A supported by the retard holder 60. In other words, the retard roller 53 is rotatably supported by the retard holder 60 via the rotation shaft 53A. The retard holder 60 has an arm 64 that extends from the accommodating portion 61 to the downstream side in the sheet conveying direction by the feed roller 52. A swing shaft 65 is formed integrally with the arm 64. That is, the swing shaft 65 is located downstream of the feed roller 52 in the sheet conveying direction.

  The swing shaft 65 is inserted through a shaft hole (not shown) provided in the internal frame of the housing 11 (see FIG. 2). Thereby, the retard holder 60 is supported so as to be swingable about the swing shaft 65. In the present embodiment, the retard holder 60 has a first position (position shown in FIG. 4A) where the retard roller 53 can contact the outer peripheral surface (roller surface) of the feed roller 52 to form the nip portion 79. The retard roller 53 is supported so as to be able to swing between a second position (a position shown in FIG. 4B) that is separated from the outer peripheral surface of the feed roller 52. In FIG. 3, the retard roller 53 at the second position is indicated by a broken line.

  The coil spring 72 applies a biasing force to the retard holder 60, one end of which is attached to the lower portion of the accommodating portion 61 of the retard holder 60 and the other end is attached to the internal frame of the housing 11. . In the present embodiment, the coil spring 72 is used as a so-called compression spring. Therefore, the coil spring 72 is attached in a compressed state from the natural length. As a result, the coil spring 72 applies a biasing force to the retard holder 60 that biases the retard holder 60 from the second position toward the first position. Note that various types of biasing members can be used instead of the coil spring 72 as long as the retard holder 60 is elastically biased from the second position toward the first position.

  In the present embodiment, when an instruction to start a paper feeding operation is input to the image forming apparatus 10, the feed roller 52 and the pickup roller 51 are driven to rotate and the paper is fed from the paper feed cassette 30. The When the paper fed from the paper feed cassette 30 by the pickup roller 51 reaches a position where the paper can be fed by the feed roller 52, the paper is further conveyed downstream by the feed roller 52 in the sheet conveying direction.

  On the other hand, when a plurality of sheets are bundled and fed by the pickup roller 51 and the leading end of the sheet bundle reaches the nip portion 79, the uppermost sheet P1 of the sheet bundle (see FIG. 4) The feed roller 52 comes into contact with the upper surface, and the retard roller 53 comes into contact with the lower surface (back surface) of the lowermost paper P2 (see FIG. 4) of the paper bundle. When the feed roller 52 is rotationally driven in this state, the uppermost sheet P1 is fed in the sheet conveying direction by contact friction received from the feed roller 52. On the other hand, the frictional force (inter-sheet frictional force) between the paper P1 and the paper P2 in the paper bundle is smaller than the contact friction between the paper P2 and the retard roller 53 and smaller than the torque set value Ft. In other words, the torque set value Ft is larger than the inter-paper friction force and smaller than the contact friction between the paper P2 and the retard roller 53. Therefore, when the sheet bundle is fed into the nip portion 79, the retard roller 53 stops without being driven. The sheet bundle sent to the nip 79 is separated from the sheet bundle only by the uppermost sheet P1 at the nip 79 and is conveyed in the sheet conveying direction by the feed roller 52, and the lower sheet P2 is conveyed. Is not conveyed forward from the nip portion 79 due to the frictional force with the stopped retard roller 53.

  When the leading edge of the sheet P1 reaches the registration roller pair 29 arranged on the downstream side in the sheet conveyance direction with respect to the feed roller 52, the rotational driving of the driving roller 29A of the registration roller pair 29 is started at that timing. The paper P1 is transported downstream in the sheet transport direction, while the rotational driving of the pickup roller 51 and the feed roller 52 is stopped. However, the pickup roller 51 and the feed roller 52 are driven by receiving frictional force from the paper P <b> 1 conveyed by the registration roller pair 29. Whether the leading edge of the sheet P1 has reached the registration roller pair 29 is determined based on, for example, a sensor signal from a sheet sensor (not shown) provided on the downstream side of the registration roller pair 29 in the sheet conveyance direction. The control unit 2 performs this. Alternatively, the control unit 2 determines whether or not the leading edge of the paper P <b> 1 has reached the registration roller pair 29 based on the paper conveyance amount calculated from the rotation speed from the rotary encoder provided in the feed roller 52.

  By the way, when the sheet bundle is fed into the nip portion 79, the retard roller in a state where the leading end of the sheet bundle is applied to a part of the nip portion 79 (the upstream end portion in the sheet conveying direction in the nip portion 79). 53 follow-up may stop. In this case, the uppermost sheet P1 is separated from the sheet bundle and conveyed by the rotation of the feed roller 52. At this time, when the uppermost sheet P1 is conveyed by the feed roller 52, the lower surface of the uppermost sheet P1 is placed on the outer peripheral surface of the retard roller 53 at the downstream end of the nip portion 79 in the sheet conveying direction. Will be in contact. For this reason, when the uppermost sheet P1 reaches the registration roller pair 29 and is conveyed so as to be pulled by the registration roller pair 29, the lower surface of the uppermost sheet P1 and the outer peripheral surface of the retard roller 53 are in sliding contact. Stick slip occurs, and noise due to the stick slip occurs.

  In order to prevent the noise, in this embodiment, the retard roller 53 is configured to be separated from the feed roller 52 when the registration roller pair 29 transports the paper P1 (see FIG. 4). That is, when the control unit 2 determines that the leading edge of the sheet P1 has reached the registration roller pair 29, the retard roller 53 is separated from the feed roller 52.

  Specifically, as shown in FIG. 3, a solenoid 90 (an example of the electric drive unit of the present invention) is attached to the retard holder 60. The solenoid 90 has a plunger 91. In order to apply the driving force of the solenoid 90 to the retard holder 60, the distal end of the plunger 91 is attached to the fixing portion 66 of the retard holder 60 via the link member 92. The fixing portion 66 is integrally provided at the rear end portion of the lower portion of the housing portion 61. The displacement mechanism of the present invention is specifically realized by the solenoid 90 and the link member 92.

  The solenoid 90 holds a retard holder 60 at the one position when the paper P1 is transported by the feed roller 52, and a driving force that displaces the retard holder 60 to the second position when the paper P1 is transported by the registration roller pair 29. Give. Specifically, the drive of the solenoid 90 is controlled by the control unit 2 (see FIG. 2). The control unit 2 outputs a drive signal to the solenoid 90 after determining that the leading edge of the paper P <b> 1 has reached the registration roller pair 29. When the drive signal is input from the control unit 2 to the solenoid 90, an electromagnetic force acts to pull the plunger 91 into the interior. Accordingly, the fixing portion 66 is pulled rearward by the link member 92, and the retard holder 60 is displaced from the first position to the second position against the urging force of the coil spring 72. On the other hand, when the drive signal from the control unit 2 is interrupted, the plunger 91 protrudes to the original position by the built-in compression spring. As a result, the link member 92 moves the fixing portion 66 forward, and the retard holder 60 is displaced from the second position to the first position by the biasing force of the coil spring 72 and is held at the first position. As a result, abnormal noise that occurs when the lower surface of the uppermost sheet P1 and the outer peripheral surface of the retard roller 53 come into sliding contact with each other is prevented. Further, since the retard roller 53 is separated from the feed roller 52, wear of the retard roller 53 is reduced.

  However, if the feed roller 52 and the retard roller 53 are separated from each other during the transport operation of the paper P1 by the registration roller pair 29, the paper P1 is being transported due to the inter-paper friction along with the transport of the uppermost paper P1 by the registration roller pair 29. There is a possibility that the lower paper P2 than the uppermost paper P1 may be pulled out from the feed roller 52 to the downstream side in the sheet conveying direction. When the lower side paper P2 is pulled out to the registration roller pair 29, the paper P1 and P2 are double-fed by the registration roller pair 29. Therefore, in this embodiment, in order to prevent double feeding of the sheets P1 and P2 by the registration roller pair 29, the retard holder 60 is provided with a stopper 70 for stopping the lower sheet P2 from being pulled out (the stop member of the present invention). An example) is provided.

  As shown in FIG. 3, the stopper 70 is provided at the upper end portion of the arm 64 of the retard holder 60. When the retard holder 60 is positioned at the second position (see FIG. 4B), the stopper 70 moves from the feed roller 52 in the sheet conveyance direction along with the conveyance of the uppermost sheet P1 by the registration roller pair 29. This is to stop the lower sheet P2 than the uppermost sheet P1 drawn to the downstream side.

  Specifically, the stopper 70 is a protruding piece that protrudes from the upper end of the arm 64 toward the conveyance path 26. In the present embodiment, the stopper 70 protrudes in a direction perpendicular to the extending direction of the transport path 26 in a state where the retard holder 60 is located at the second position, and its tip reaches the vicinity of the center of the transport path 26. ing. Therefore, in the conveyance path 26 on the downstream side of the feed roller 52, there is a gap between the tip of the stopper 70 and the upper conveyance guide surface 26A.

  The stopper 70 is provided downstream of the swing shaft 65 in the sheet conveying direction, that is, on the rear side. Therefore, in the state where the retard holder 60 is located at the first position, the stopper 70 assumes a tilted posture (posture shown in FIG. 4A) tilted backward with respect to the direction orthogonal to the transport path 26.

  Since the feeding mechanism 50 configured as described above is provided in the paper feeding device 24, when the feed roller 52 is rotated in a state before the paper enters the nip portion 79, the retard roller 53 becomes the feed roller. A force equal to or greater than the torque set value Ft is applied by the contact friction with 52, and the feed roller 52 is driven to rotate.

  Further, when a plurality of sheets are sent out in a bundle by the pickup roller 51 and the sheet bundle enters the nip portion 79, the retard roller 53 stops without being driven and rotated by the influence of the inter-sheet friction. On the other hand, the uppermost paper P1 on the feed roller 52 side is separated from the other lower paper P2, and only the uppermost paper P1 is conveyed by the feed roller 52. At this time, the elastic member 58 of the retard roller 53 is pressure-deformed by the feed roller 52, and the nip portion 79 is formed in a downward arc shape. When the paper P1 is conveyed by the feed roller 52, the paper P1 is conveyed while being curled upward by the arc-shaped nip portion 79. Therefore, the paper P1 that has passed through the nip 79 is in a state where the leading end is curled upward. As a result, the paper P1 passes through the gap between the stopper 70 and the upper conveyance guide surface 26A without contacting the stopper 70.

  When the paper P1 reaches the registration roller pair 29 and is transported, the control unit 2 outputs the drive signal to the solenoid 90 to operate, thereby displacing the retard holder 60 from the first position to the second position. Let Further, the rotational driving of the feed roller 52 and the pickup roller 51 is stopped. At this time, the lower sheet P2 is pulled out toward the registration roller pair 29 as the uppermost sheet P1 in the sheet bundle is conveyed, but the pulled sheet P2 is pressed down against the upper sheet P1. While moving, it moves along the upper end of the arm 64. For this reason, when the paper P2 is pulled out to the stopper 70 existing at the movement destination, the leading end of the paper P2 comes into contact with the stopper 70 and further movement is restricted. That is, the movement of the paper P2 is stopped by the stopper 70. Thereby, since the paper P2 does not move to the registration roller pair 29, the double feeding by the registration roller pair 29 is prevented.

  Thereafter, when the trailing edge of the sheet P1 passes through the feed roller 52 and the next sheet P2 is conveyed, the control unit 2 stops the drive signal and stops the driving of the solenoid 90. Thereby, the retard holder 60 is returned from the second position to the first position. After that, the control unit 2 restarts the rotational driving of the feed roller 52 and the pickup roller 51, and starts conveying the next sheet P2. At this time, the leading edge of the sheet P2 is in contact with the stopper 70, but with the retard holder 60 positioned at the first position, the stopper 70 is tilted (position shown in FIG. 4A). It has become. Therefore, when a conveyance force is applied to the paper P2 from the feed roller 52, the leading edge of the paper P2 easily passes over the stopper 70 and is conveyed toward the registration roller pair 29.

  As described above, according to the paper feeding device 24 of the present embodiment, it is possible to suppress abnormal noise during paper conveyance, and after the retard roller 53 is separated from the feed roller 52 and the nip portion 79 is released. It is possible to prevent double feeding of paper by the registration roller pair 29.

  In the above-described embodiment, the configuration realized by the solenoid 90 and the link member 92 is illustrated as an example of the displacement mechanism, but the displacement mechanism of the present invention is not limited to this configuration. For example, as shown in FIG. 5, the displacement mechanism of the present invention is provided with a torque limiter 84 inside the drive roller 29 </ b> A of the registration roller pair 29, and the torque limiter 84, the transmission mechanism 80, and the link member 92. It may be realized. Here, the transmission mechanism 80 is a gear transmission mechanism including a plurality of gears 81 that transmit the rotational driving force of the driving roller 29 </ b> A to the retard holder 60. An engagement shaft 82 is provided on the side surface of the gear 81 on the retard holder 60 side of each gear 81, and the engagement shaft 82 is connected to the link member 92. Thus, when the drive roller 29A is rotationally driven, each gear 81 is rotated, and the rotational driving force is transmitted to the link member 92 via the engagement shaft 82, so that the retard holder 60 is moved to the first position and the second position. Displace between positions. In addition, since the torque limiter 84 is provided in the drive roller 29A, the torque limiter 84 rotates idly when a torque having a magnitude greater than a predetermined torque setting value is applied to the link member 92. For this reason, it is possible to prevent the link member 92 from being damaged by applying a torque larger than necessary to the link member 92.

4: Image forming unit 10: Image forming apparatus 24: Paper feeding device 26: Conveying path 29: Registration roller pair 29A: Driving roller 30: Paper feeding cassette 50: Feeding mechanism 51: Pickup roller 52: Feed roller 53: Retard roller 58: Elastic member 60: Retard holder 64: Arm 70: Stopper 74: Torque limiter 79: Nip portion

Claims (6)

A sheet accommodating portion capable of accommodating a plurality of sheets;
A first conveying roller that conveys the sheet in the sheet conveying direction by being rotationally driven in contact with the sheet fed in a predetermined sheet conveying direction from the sheet storage unit;
The uppermost sheet is provided from a sheet bundle made up of a plurality of sheets, which is provided below the first conveying roller and is in contact with the first conveying roller to form a nip portion and is fed from the sheet storage unit. A separation roller for separation at the nip,
A conveyance path extending from the nip portion to the downstream side in the sheet conveyance direction;
The separation roller is rotatably supported, and the separation roller comes into contact with the first conveyance roller around the swing shaft positioned downstream of the first conveyance roller in the sheet conveyance direction. A support member supported so as to be swingable between a first position where a part can be formed and a second position where the separation roller is separated from the first transport roller;
A second conveying roller that is provided downstream of the first conveying roller in the sheet conveying direction and conveys the sheet conveyed by the first conveying roller by being driven to rotate in the sheet conveying direction;
A displacement mechanism that displaces the support member to the first position during a transport operation by the first transport roller and displaces the support member to the second position during a transport operation by the second transport roller ;
The support member is
An arm extending downstream in the sheet conveying direction and provided with the swing shaft;
The arm is provided at an upper end portion on the transport path side, and protrudes from the upper end portion toward the transport path in a state where the support member is located at the second position, and the support member is Lower than the uppermost sheet pulled out from the first conveying roller to the downstream side in the sheet conveying direction when the uppermost sheet is conveyed by the second conveying roller when displaced to the second position. the conveyance of the sheet has a stop member for stopping, and
The stop member is
When the lower sheet moves along the upper end portion of the arm while being pressed downward by the uppermost sheet, the lower sheet moves by abutting against the tip of the lower sheet. Regulating sheet transport device. The sheet conveying apparatus according to claim 1, wherein the stop member is a protruding piece that protrudes from the upper end toward the conveying path in a state where the support member is located at the second position. The sheet conveying apparatus according to claim 2, wherein the stop member is provided in the arm on a downstream side of the swing shaft in the sheet conveying direction. The displacement mechanism holds the support member at the first position during a transport operation by the first transport roller, and applies a driving force to displace the support member to the second position during a transport operation by the second transport roller. The sheet conveying apparatus according to any one of claims 1 to 3, further comprising an electric drive unit. The displacement mechanism is
A transmission mechanism for transmitting the rotational driving force of the second transport roller to the support member;
A torque limiter provided in the transmission mechanism and idling when receiving a set torque that is equal to or greater than a predetermined set value, and the support member is displaced to the second position by the set torque. The sheet conveying apparatus according to any one of 3. A sheet conveying device according to any one of claims 1 to 5;
An image forming apparatus comprising: an image forming unit that forms an image on the sheet conveyed by the sheet conveying apparatus.

Images